8 THE BIRTH OF THE STEAM ENGINE. imperishable fame: we mean the employment of Steam as a motive force, as a mechanical agency-an idea which had been suggested to his fertile mind by his friend Robison's experiments on the practicability of adapting it to the propulsion of wheel-carriages. He had not pushed his inquiries very far, however, when, in the winter of 1763, a small model of Newcomen's steam-engine was placed in his hands for repair. This was the spark which fired the train. This was the opportunity which comes to everyone of us, sooner or later, but which few men have the courage to seize and the ardour to improve as Watt did. His attention was now completely arrested, and from that fortunate hour to the end of his long and useful career, Watt's active mind and keen sagacity were devoted to the development of the motive powers of steam. 3. And here we must pause to sketch, very briefly, the progress of the steam engine from its first feeble outlines up to the time that Watt's intuitive sagacity recognised its possible usefulness. Solomon de Caus, a French engineer, published, in 1623, a volume of curious interest, in which is shadowed out the earliest rude conception of the expansive powers of vapour. He proposed the insertion of a perpendicular tube in a vessel of boiling water, nearly to the bottom, that through this tube might ascend the steam which the heat would throw off. A constant supply of water was obtained through a tap in the side of the vessel. 4. Forty years later, the ingenious and loyal Marquis of Worcester published his famous 'Century of Inventions,' and among its various scientific problems appears (No. 68) 'An Admirable and Most Forcible Way to Drive up Water by Fire.' The peer's mechanism was founded upon the same principles as De Caus had enunciated. But De Caus had only theorised. The Marquis carried theory into practice, and advanced from speculation to experiment. He actually constructed an apparatus which, he says, forced water up to a height of 40 feet. To him, therefore, the honour must be ascribed of having erected, rude and imperfect as was the model, the First Steam Engine. ITS GRADUAL GROWTH. 5. Sir Samuel Morland, who was not only an able diplomatist but a skilful mechanician, added, about 1683, another fragment of experimental knowledge to the scanty store which the primitive fathers of the steam engine had slowly amassed. He pointed out the vast disproportion existing between the areas respectively occupied by a certain amount of water, and the steam which that amount produced. He estimated it as 1 to 2,000-no very important miscalculation, even when compared with the more definite result obtained by later enquirers (1 to 1,750). 6. Denys Papin, a native of Blois, who came to reside in England about 1678, and occupied himself for some years in mathematical studies and pneumatic experiments, made yet another step in advance, by the introduction of 'a piston' into the tube which carried off the steam from the boiler, or cylinder. This, indeed, was a feature of Otto Guericke's air-pump, and consisted in so fitting a rod or block to a longitudinal cavity that it moved up and down with freedom, while preventing the intrusion of any extraneous substance. Introducing water into the bottom of his cylinder, and heating it by a fire underneath, Papin had the pleasure of seeing his piston impelled by the expansive force of the generated steam. He then removed his furnace -an awkward necessity- and, the steam again condensing into water, a considerable vacuum was produced, through which the piston immediately descended. 7. Captain Savery's is the next name associated with the progress of the steam engine. His invention was suggested by an accident—an accident which had probably occurred a thousand times before, but never before happened to arrest the attention of a quick and ingenious observer. At a tavern, one day, he called for a flask of Florence wine, and, having drunk its contents, flung the empty vessel upon the fire. Soon afterwards he perceived that the heat had expanded into vapour, the drops of wine still adhering to its sides; and snatching it from the fire, while thus filled, he plunged it, mouth downwards, into a basin of cold water. A vacuum was instantly produced by the condensation of the steam, and the cold water rose within the 10 THE SAFETY VALVE. flask. Savery seized upon this fact, deduced from it an inference, and applied that inference to a practical purpose. Creating a vacuum within a cylinder, he raised water to its level, and then directed it into another vessel, employing the expansive power of steam to force it to a considerable height. Thus he was enabled to construct an apparatus or forcing pump, still occasionally used, for the supply of stately mansions, or garden fountains, or artificial lakes, with water. 8. Dr. Desaguliers, in the year 1718, improved upon Savery's machine, by the application of the safety-valvean idea which, in a somewhat different form, had suggested itself to Papin. The utility of the safety-valve is this: it is so weighted that up to a certain point it successfully resists the expanding force of steam, but when that point is passed, it spontaneously gives way, and suffers the giant element to escape before it can shatter into fragments the cylinder that would vainly seek to imprison it. For unless you vigilantly guard your Frankenstein, the monster will rend into pieces the magician who called him into being! Desaguliers also invented a new method of condensation by injecting a stream of cold water within the boiler, instead of applying it externally in the cumbrous and extravagant way which Savery had adopted. 9. But the steam-engine owes more to Newcomen than to either of its previous patrons. This clever mechanician was a native of Dartmouth, and in himself affords an interesting example of the success which crowns the zealous devotion of one's powers to the fulfilment of a cherished ambition. He early addicted himself to scientific studies. In his later investigations into the capabilities of steam he was assisted by another ingenious Dartmouth mechanic, one John Calley, a glazier; and the two constructed an engine upon Papin's principle-the piston rising through the expansion of the steam, and descending through the pressure of the external air; but they improved upon Papin and Savery, by introducing a jet of water into the cylinder, as Desaguliers had done. Their discovery, however, was made independently of him, and in ignorance that it had THE ATMOSPHERIC ENGINE. 11 occurred to any previous inventor. It is said to have been suggested to them by the accident of some water trickling into the cylinder through a hole which attrition had wrought in the piston. Wonderful faculty of Genius!—to seize upon the trifles unconsidered by ordinary minds, and educe from them the sublimest results! Is it not the true type of the mythic Midas, which changes all it touches into gold? Newcomen's engine was really an atmospheric one, for steam was only employed to produce the vacuum in the cylinder, and the pressure upon the piston was furnished by the atmosphere: a pressure which, with the most perfect mechanical contrivances, does not exceed 15 lbs. to every square inch. Nevertheless, its utility, in those days of imperfect scientific knowledge, was unquestionably considerable, and its inventor deserved the reputation he obtained. It soon underwent improvement at the hands of Potter and Beighton. Potter was a lad employed upon one of these engines to open and close the valves which alternately admitted water and steam, but, being of a playful disposition, contrived, by fastening the valve-handles with string to certain cranks and levers, to make the engine do its own work. Beighton, an able engineer, afterwards perfected this ingenious contrivance, and Newcomen's engine was then (A.D. 1718) as complete as it could well be made. Having summarised thus rapidly the early annals of the stcam-engine, we return to our review of James Watt's laborious career: 10. So numerous were the defects in the models of Newcomen's engine which had been intrusted to him for repair, that Watt's powers of investigation were completely aroused. He carefully examined its mode of working, and soon discovered how imperfectly it fulfilled its intended object. He saw, first, that the cylinder was not of a capacity to supply steam for the creation of a proper vacuum; and, second, that such power as the engine did possess was not judiciously economised. Carrying his researches farther, he began to inquire whether greater results ought not to flow from the employment of so potent 12 THE CONDENSING ENGINE. a slave, and instituted a series of ingenious experiments upon the characteristics and properties of this new motive force. Thus, he constructed a boiler which showed, on inspection, the amount of water evaporated in a given time, and he ascertained that the rapidity of its evaporation was regulated by the extent of surface-heat applied to the water, . . . that steam would heat six times its weight of spring-water up to its own temperature, or 212° Fahrenheit. - a 11. Having prepared himself for his self-imposed task by the most comprehensive investigations, unconsciously observing the maxims of that inductive philosophy which Bacon established upon the ruins of the Stagyrite's visionary theories, Watt now proceeded to consider how the defects of Newcomen's engine might be amended. One radical fault was its imperfect employment of the motive power of the steam. Every time cold water was injected, not only was the steam condensed, but the cylinder cooledmanifest waste of heat and power. Watt's intellect was busy for many an anxious hour in designing remedies for this cardinal deficiency. At last there occurred to him, while taking one afternoon his customary exercise, an expedient of exquisite simplicity, which nevertheless removed every difficulty; namely, to draw off the steam from the cylinder and condense it in another vessel. In one or two days, he says, the entire details of the necessary mechanical agencies were arranged in his mind, and he had conceived the main features of the present condensing steam engine. . . an invention whose beneficial influence upon the history of our race can hardly be over-estimated. Connect the cylinder by an open pipe with another vessel, and the elastic vapour will immediately flow from the former, as soon as admitted into the latter, where, subjected to the action of cold water, it will at once condense. A vacuum thus created, more steam will be instantly supplied by the cylinder; and this movement will continue, until the cylinder has been completely emptied without exposure to a single drop of water, the condenser alone being cooled by the cold water used to concentrate the steam. Watt |